1. Field of the Invention
The present invention relates to prefabricated modular structural members and especially those to be used within low-cost construction.
2. Description of the Prior Art
The prefabrication of structural members to be incorporated within a modular structure has in recent history begun to enable adequate low-cost construction providing, for example, low-cost housing development. As the art of prefabrication matures, the problems to be addressed include the enhancement of the structural properties of the independent modular members and of the assembled structure as a whole while keeping production and labor costs at a minimum.
The early development of prefabricated structural members provided for little or no structural support, as in U.S. Pat. No. 3,717,672 wherein a non-load-bearing drywall partition is disclosed. The drywall partition of the disclosure is intended for rapid assembly and removal of a temporary internal partition and addresses no further structural problems.
U.S. Pat. Nos. 3,246,058 and 3,555,756 concern themselves with foamed plastic-filled insulating panels and the methods for producing them. These patents do not disclose panels or structural members which in combination are capable of providing the structural framework required for a modular structure. U.S. Pat. No. 3,246,058 makes no reference to the incorporation of the disclosed foam sandwich structures within a modular construction. The panel unit disclosed in U.S. Pat. No. 3,555,756 depends upon a preassembled building structural framework in order to be incorporated within a structure.
The production of the panels disclosed in these patents relies heavily upon expensive machinery, semi- or fully-automated, and upon the high-cost labor required to operate such machinery. In addition, the panels produced provide no accommodation for the passage of utility lines such as piping or electrical conduit throughout the walls of a modular structure.
The structural member of U.S. Pat. No. 4,052,828 discloses a sandwich panel comprising outer drywall boards sandwiching a vertically-disposed accordion-pleated cardboard core. While the insulating and acoustical properties of the disclosed structural member are more or less adequate, the configuration of the device provides a structural fire hazard in that it allows and indeed encourages chimney updraft within the core of the structural member owing to the vertical disposition of the accordion-pleated core. The cardboard core even though treated for water and fire resistance is still, especially over a period of time within a modular structure, susceptible to waterlogging or combustion. Adequate water or fireproofing undermines whatever cost advantage is gained by the utilization of a cardboard core. Alternate embodiments disclosed of the structural member in U.S. Pat. No. 4,052,828 replace the pleated core with plastic or metal material raising the cost of the structural member. Although the plastic pleating would be less expensive than the sheet metal pleating, the consequences in terms of both structural collapse and occupant safety of the plastic melting during a fire are far from desirable. Only the vertical pleated sheet metal embodiment disclosed would provide any real vertical beam support and the excessive utilization of expensive sheet metal material renders that embodiment of the structural member economically untenable for use in a low-cost construction situation. The vertical disposition of the pleated core does not facilitate the required horizontal passage of utility lines throughout the interior of the walls of a modular structure. Finally, the accordion pleating of the core allows for very limited contact area for attachment to the outer paneling.
Applicant is aware of no adequate low-cost, low-maintenance, fire-resistant modular structural members having good insulating and acoustical properties which also allow and accommodate the passage of utility lines throughout the walls of a modular structure which do not require expensive machinery for manufacture and which may be assembled either on-site or in an off-site factory situation.